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Updated: Aug 12, 2026

Fecal Glucocorticoid Analysis: Non-invasive Adrenal Monitoring in Equids
Published on: April 25, 2016
18-Hydroxycorticosterone as a marker for primary hyperaldosteronism
R Lapworth1, F Short, V H James
1Department of Chemical Pathology, St Mary's Hospital, London, UK.
Abstract:
An assay for the measurement of 18-hydroxycorticosterone (18-OHB) in plasma has been validated. The method involves extraction of plasma with dichloromethane, thin layer chromatography and radioimmunoassay with an iodinated 18-hydroxycorticosterone-3-carboxymethyloxime ligand. The plasma concentration of 18-OHB was measured in 16 patients with primary hyperaldosteronism and 20 control subjects. After overnight recumbency a significantly higher mean concentration of 18-OHB was found in the samples taken from the patients than in those from the control subjects. The degree of elevation did not clearly discriminate between patients with a unilateral adenoma and those with bilateral adrenal hyperplasia. A significant anomalous postural decrease in the 18-OHB concentration occurred in 10 of the 13 patients with an adenoma, whereas there was a significant postural increase in the three patients with hyperplasia.
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